X-ray microscope (detail)

Inner view of an X-ray microscope: image quality indicators of different sizes with gold structures down to 500 nm (foreground) and high power microfocus X-ray tube with filter wheel (background).

Source: BAM

Project period

01/07/2019 - 30/06/2022

Project type

EU project

Project status



NanoXSpot is a European-wide joint research project that will develop traceable measurement methods determining the focal spot size, shape, and position of X-ray tubes with spot sizes down to 100 nm.


Bundesanstalt für Materialforschung und -prüfung
Unter den Eichen 87
12205 Berlin

Cathode (Wehnelt cylinder and filament) of a micro focus X-ray tube

Cathode (Wehnelt cylinder and filament) of a micro focus X-ray tube

Source: BAM

Besides medical applications, X-ray-based computed tomography (CT) systems are increasingly used in industries such as aerospace for non-destructive testing purposes and for the evaluation of defects and inner structures. These industries require inspection resolutions at the nanometre scale. The overall aim of this project is to develop traceable measurement methods for determining the focal spot size, shape and position of nanometre resolution X-ray tubes

Ein Pfeil in der Mitte einer Zielscheibe

Source: BAM

The overall objective of the project is to develop a traceable method for the measurement of focal spot sizes in the nanometre range and providing a draft standard to be submitted to CEN/TC 138/WG 1.

Stilisierter Programmablaufplan

Source: BAM

Computed tomography (CT) methods and modulation transfer function measurements will be applied and analysed for the characterisation of nanometre X-ray tube spot sizes. The analyses are based on radiographs of high precision nanometre gauges. The considered methods for the characterisation of these structured gauges are different traceable types of microscopy methods (AFM, SEM, TEM) and micro CMM.


Source: BAM


4 Metrological Institutes from 3 European countries, CEA LIST Institute from France, 5 industrial partners from 2 European countries and one from the USA


Bundesanstalt für Materialforschung und -prüfung (BAM)


The project receives funding from the European Metrology Programme for Innovation and Research (EMPIR).


NanoXSpot aims to establish an internationally accepted standard for the characterisation of X-ray tubes in the nanometre region which is applied all over the world and which ensures the comparability and quality of these products on the global market.


Within the NanoXSpot project, a traceable measurement method will be developed for determining the spot size, shape, and position of X-ray tubes from 100 nm to 5 μm including the uncertainty of measurements below 10% (precision and bias). Traceable methods are needed with uncertainties below 5% to characterise nanometre gauges (line pattern and edge structures) which are used to measure the focal spot characteristics. A numerical algorithm will be developed for the determination of the spot parameters from nanometre gauge measurements. This also includes a software implementation of the algorithm. To evaluate other parameters affecting the spot, numerical modelling will be used. For the validation of the developed methods inter- and intra-laboratory comparisons will be performed. Furthermore, the new method will be incorporated into a draft standard on the characterisation of X-ray tubes with focal spot sizes smaller than 5 μm which is going to be submitted to CEN/TC 138/WG 1 and later to ISO/TC 135/SC 5.

Dr. Gerd-Rüdiger Jaenisch and full view of an X-ray microscope

Dr. Gerd-Rüdiger Jaenisch and full view of an X-ray microscope with microfocus X-ray tube (left), sample holder (center), digital detector array and objective beamlines (right).

Source: BAM

Technical Work Packages

The NanoXSpot project consists of 4 technical work packages (WP) in addition to an impact work package as well as a work package for management and coordination.

Development and investigation of different measurement principles for focal spot sizes below 5 μm

The aim of WP1 is to propose an appropriate measurement procedure for focal spot sizes below 5 μm based on available line and hole gauges. The evaluation will include real measurements with different X-ray sources using the same setup as well as a comparison with standards for the measurement of focal spot sizes beyond 5 μm.

Dimensional metrology of nanometre gauges

The aim of WP2 is to provide traceable methods to characterise nanometre gauges which are used for the measurement of the spot size, shape, and position in the range between 100 nm to 5 μm. The target uncertainty for the spot size measurement shall be better than 10 %. The selected structures will be prepared for measurements and evaluated accordingly. Uncertainties will be estimated for all conducted measurements.

Numerical algorithms for spot size image evaluation and optimisations through simulation tools

The main objective of WP3 is to implement numerical algorithms for the determination of the focal spot size, shape and position. Those algorithms will be integrated into a stand-alone software tool which is made available for public use. In order to support the development and to evaluate the limits of the algorithms, available simulation tools will be used.

Validation of the developed measurement method

The aim of WP4 is to validate the developed measurement method and make recommendations outlining key points for method description and application. The validation procedure will primarily test the reproducibility and repeatability of results across different operators on various systems. Based on these results a new draft standard will be developed.


BAM Bundesanstalt für Materialforschung und -prüfung (BAM), Germany

Project partners

METAS Eidgenössisches Institut für Metrologie, Switzerland

VTT Teknologian tutkimuskeskus VTT Oy, Finland

CEA Commissariat à l'énergie atomique et aux énergies alternatives, France

Excillum AB, Sweden

KOWOTEST Gesellschaft für Prüfausrüstung GmbH, Germany

X-RAY WorX GmbH, Germany

PTB Physikalisch-Technische Bundesanstalt (PTB), Germany

YXLON International GmbH, Germany

Carl Zeiss X-Ray Microscopy, Inc., Germany


The project receives funding from the European Metrology Programme for Innovation and Research (EMPIR) which is an integrated part of Horizon 2020, the EU Framework Programme for Research and Innovation.


Source: EMPIR